trying to copy 1 hard drive to another

I think you need to supply a little more information about what kind of devices and what you've tried.

I assume you have both devices plugged in to your Mac?

Do they both show up in the finder/on the desktop.

If the device you are trying to copy to is formatted as NTFS, then you won't be able to write anything to it directly from the finder - as OSX only supports reading of NTFS volumes, not writing. You can do it, by installing some extra components.

- barry

I'd say it's formatted in NTFS. You can check the partition type by running Disk Utility, and selecting your drive, and the partition section.

You'll need to reformat it if you want to write to it from your Mac, unless you want to install some additional software to write to NTFS disks (google for it) Be aware that formatting will completely erase it.

If you're only going to use it on a Mac, then Mac OS Extended format would be best. If you'll need to share it with a PC at some point, then FAT would be best.

FAT32 has some limitations including a max file size of 4GB I think. FAT64 or exFAT is a newer version, that will work with Snow Leoparad 10.6.5 or later and with Windows Vista SP1 or later.

- barry

You need to reformat your drive so you can write ( from the Mac ) to it.
You need to use the Disk Utility application to format.
You need to decide if you want to use both Mac and PC to write to the drives hence the mention of NTFS/FAT32/Mac OS Extended ( different ways of formatting)